Asymmetric intermolecular Pauson-Khand reaction of symmetrically substituted alkynes.

The asymmetric intermolecular Pauson-Khand reaction of symmetric alkynes has been accomplished for the first time. N-Phosphino-p-tolylsulfinamide (PNSO) ligands have been identified as efficient ligands in this process. The chirality of the cobalt S-bonded sulfinyl moiety was found to direct olefin insertion into one of the two possible cobalt-carbon bonds in the alkyne complex. Reaction of symmetric alkynes allows for a simplified experimental protocol since there is no need for separation of diastereomeric complexes.